Further to the wreck of Erika, a network of benthic monitoring called REBENT was set up within the framework of the State-Region Plan / region Brittany in 2003. The pilot program REBENT-Bretagne had for objectives to acquire a relevant and coherent knowledge of coastal benthic habitats, and to establish a surveillance system, in order to detect the medium and long-term evolutions, in particular as regards the biological diversity. This program was the basis of reflection for the implementation of a network of benthic monitoring within the framework of the European Water Framework Directive (WFD), set up in 2007. The regulatory aspect of the WFD allows to assure the sustainability of a network of benthic monitoring on the coastal facades of France. This directive gives, at the european scale, an objective of environmental quality that allow for the development (or maintenance) of aquatic resources and the satisfactory functioning of the ecosystem. It can generate, given the state of the environment, programs to restore or protect biological integrity. The idea of `quality' of benthic communities implies the definition of reference conditions that will serve as a standard for detecting causes and levels of degradation of the communities studied.

Characterizing the condition of benthic communities and predicting their spatio-temporal evolution requires the development of assessment methods. This approach is based, through research and expertise, on the use of biological indicators, biotic indices or better multimetric or multicriteria approaches, which make assessments more relevant. In response to the Water Framework Directive (WFD), France has chosen to retain the multivariate AZTI Marine Biotic Index (M-AMBI) as an index for classifying the ecological state of water bodies through the benthic macroinvertebrate of soft substrates (MIB) parameter on the English and North-East Atlantic facades (Decision 2005/646/EC, JOUE No L 243 of 19 September 2005).

The WFD is based on a stational approach, characterized by monitoring different subtidal habitats according to a hierarchical sampling protocol. Habitats selected are ecologically important façade-scale habitats. The main objectives of this approach are to:

• describe the medium- and long-term changes in coastal benthic ecosystems, whether natural or anthropogenic,
• characterize these changes qualitatively (specific composition) and quantitatively (abundance and biomass) in order to assess the health status of the environment,
• help explain these changes by considering the relative shares of natural and/or anthropogenic variability of local, regional or global origin.